Treatment of waste saltwater to reduce volume is becoming increasingly important, particularly for mining, oil and gas, and inland desalination systems. Mines can produce tailings water, which is typically ponded. Oil and gas operations can produce saltwater with the hydrocarbon reserve or during processing. Desalination is being increasingly used in both industries as regulations require treatment of impaired water. Desalination is also used in coastal regions to produce freshwater from seawater, with the more saline brine reject returned to the ocean. Inland brackish water can be desalted, however there is often no convenient way to dispose of the brine reject. Common brine reject management options include discharge to a sewer or the environment, ponding, deep well injection, or treatment to produce solid salt in concentrators and crystallizers. The first two methods are becoming more challenging due to tightening environmental regulations and cost. Concentrators and crystallizers are used to distil water and produce solids, which can then be land filled or put to secondary use, yet they suffer from high capital and energy cost. Capital costs are high due to the extensive use of alloyed steels and titanium required at the operating temperatures and pressures. Energy costs are high due to the use of large volume compressors, which on average consume 20 to 60 kWh of electrical-mechanical power per cubic meter treated. Steam vapour compressors may be used, which consume higher quality steam in place of mechanical power. The cost of brine management is largely proportional to the volume of brine requiring treatment. It is therefore beneficial to devise a plant to treat saltwater to reduce volume and preferably produce solids. Consequently, there is a need for an alternative method and apparatus for concentrating solutions, such as desalinating saltwater.
As saltwater solutions are concentrated, salts can precipitate and scale on various process components. When scaling occurs, performance of the system can quickly diminish. The most common reoccurring maintenance required in any humidification driven saltwater concentrating system is de-scaling the system components. Therefore, there is also a need to devise a system that efficiently and periodically removes scaling.